a. Field of Invention
The invention relates to a system and method for specifying and positioning a sensor of digital X-ray apparatus.
b. Description of Related Art
The production of digital intraoral images using an intraoral sensor is disclosed in EP 0 643 901 (U.S. Pat. No. 5,513,252). The features disclosed in said document are incorporated in this application by reference.
In the field of dental digital X-ray examination there is a large number of various sensor sizes and shapes for producing intraoral images. The selection of these sensors is usually guided by experience. Experience, however, is frequently based on invalid tests.
Thus a larger sensor might be more suitable than a smaller one in certain X-raying situations. In other cases the point to be examined would be easier to reach, from an anatomical point of view, by using a smaller sensor. Furthermore, the decision must be made as to how the desired objects can be X-rayed using a smaller sensor.
Particularly in the case of individual series of radiograms of one patient, it has previously been difficult to judge how many images should be produced and what teeth should, if possible, be X-rayed together in order to minimize the radiation impact by lowering the number of X-ray images.
It is an object of the invention to provide a system and method for simplifying the selection of sensors from the outset.
This object is achieved by a system and method having the features of the independent claims. Specifically, as shown in FIG. 2, the aforementioned objects are achieved by a system for specifying the position of a sensor 14 of a digital X-ray apparatus, which system exhibits input and output devices 8 for interactive control of the system. These devices preferably comprise a graphics system on which digitized X-ray photographs and X-ray images can be shown and keyboards and pointing devices. The system has a first storage area 9, in which a digital image of an area to be examined is stored. In this case the image is ideally an individual general image in the form of a panoramic radiogram of the patient to be examined. If no such image should be present, the system offers a selection of patterns, from which that can be selected which matches the patient best.
In a second storage area 10, which may physically coincide with the first storage area, there are stored as many template images of the sensors as there are sensors or possible arrangements of sensors. The templates are displayed such that they comply with the shape and size of the image of the relevant sensor.
Another component of the system is a processing unit 11 which places the template image of at least one sensor simulatively on the area of the digital image which is to be examined such that in the case of a real X-ray image the region to be examined is imaged completely. Said processing unit is preferably a known processor. The processor can either carry out fully automatic determination, in which case a previously specified area is covered, as a result of matching computation based on the shape and coordinates of the templates, so well that a minimum amount of radiation is necessary. Optimization is effected in observance of the criterion that the overlap should be as small as possible, for by this means the patient is exposed only to that radiation dosage which is just necessary.
The processing unit furthermore has means for displaying the sensor and the position of the sensor in the digital image, for which purpose the output device, in particular, is provided. This makes it possible for the user to ascertain the sensor specified by the processing unit, and the position of the sensor.
The system has in its preferred form a user interface 16 enabling interactive selection of the template image and/or the area to be examined. This makes it possible for the user to be interactively engaged in the specifying procedure. One possible user interface is a graphical interface of a computer on which the image is displayed. Selection boxes make it possible to select different templates, which can then be moved to the area to be examined by means of a pointing device, such as a mouse. The area to be examined must be specified for filly automatic determination. This can likewise take place by specifying points with the aid of a pointing device. In the case of completely manual selection, the digital template is passed over the area, which is then preferably displayed in a different color. It is particularly advantageous when only those objects forming part of the image which are to be examined are made particularly distinguishable, ie, for example, when only the teeth are high-lighted.
If the image should contain information concerning several dimensions, the position of the template image relative to the X-ray image can possibly be specified in one or more dimensions. To this end the image is in the form of a multidimensional object, in particular a two-dimensional area having an additional dimension determining down/up, right/left, or rotated alignment.
By way of a computer interface 12 to the X-ray apparatus the thus determined presettings are transferred to the X-ray apparatus, which permits the production of a digital image only when these presettings prevail. Thus the X-ray apparatus can block X-raying until the correct sensor has been selected. This information can be provided by coding the sensors and using corresponding contacts in the sensor mount.
To remove the necessity of having to work with templates only, the system has a computer interface 13 via which digital images of the patient to be X-rayed are transferred to the first storage area. This ensures that very precise presettings will be used and the selection will be matched to anatomic peculiarities.
The X-ray apparatus used is preferably a dental X-ray unit. The system is preferably in the form of a PC controlled by software, which carries the method defined in the claims stated below into effect.
Another component of the present invention comprises digital or mechanical templates for specifying a digital X-ray sensor complying in shape and size to an X-ray image made with the assigned digital X-ray sensor. This makes it possible, by mechanically shifting the template over an existing image, to ascertain what sensor will be most suitable for a future image.
The template is preferably designed such that it can be moved across an X-ray image without restricting the visible area of the image. This may be effected, for example, by the use of a frame and/or transparent material 15.
The invention also relates to a method of specifying and/or positioning a sensor of digital X-ray apparatus by means of templates complying in size and shape to the sensor image. The method has a first step in which an X-ray image is selected, this being preferably an X-ray image of the patient to be examined. In the second step, the area to be depicted is determined. This area can either be one digitally predetermined or one specified by the user by image a frame around the object to be X-rayed. In a third step, there is selected, from a plurality of templates of which each is assigned to a sensor of the digital X-ray apparatus, that template which covers the area specified in the second step most precisely. For subsequently creating the image, that sensor is selected to which the template determined in the third step is assigned.
Selection of the template may be carried out either automatically or interactively.
In a preferred embodiment, the X-ray images and the templates are managed in digital form.
The invention also relates to software for effecting the said method.
Yet another component of the invention is a data medium having a data structure that is capable of running on a computer to effect the method described above.